Spiral Growth Manufacturing (SGM) – A Continuous Additive Manufacturing Technology for Processing Metal Powder by Selective Laser Melting

Spiral growth manufacturing is a new innovative powder based rapid manufacturing technique. The innovation exists in the methodology in which powder layers are deposited. Unlike other pre-placed powder systems, the deposited layers move relative to the location at which they are processed. This is made possible by a rotating build drum into which powder is deposited, in spiralled layers, from a stationary hopper. With this configuration powder can be continuously deposited and levelled and simultaneously processed, eliminating delays in the build cycle. Stainless steel and cobalt-chrome powder is selectively melted using a 100W flash lamp pumped Nd:YAG laser. This paper reports on factors affecting build rate and on build strategies for creating a number of axis-symmetric thin and thick walled cylinders. Experimental results suggest that build rate for thin walled structures bonded to a substrate will ultimately be governed by tangential movements of the powder particles when frictional forces are not sufficient to accelerate the particles along a curved path, provided that enough laser power is available for melting. Even melt pool balling, which is evident when melting one layer at high speeds, diminishes in multiple layer builds due to re-melting and infilling.Mechanical Engineerin

The Vampire and the FOOL

This paper presents new features recently implemented in the theorem prover Vampire, namely support for first-order logic with a first class boolean sort (FOOL) and polymorphic arrays. In addition to having a first class boolean sort, FOOL also contains if-then-else and let-in expressions. We argue that presented extensions facilitate reasoning-based program analysis, both by increasing the expressivity of first-order reasoners and by gains in efficiency

Image Transformations and Printing of Plaster Layers in Spiral Growth Manufacturing

Spiral growth manufacturing (SGM) is a high speed rapid manufacturing technique in which objects are built up, layer by layer, by simultaneously depositing, levelling and selectively consolidating thin powder layers onto a rotating build platform. The size and position of the jetted droplets are mapped by the position and greyscale level of pixels within an 8 bit greyscale bitmap image. This paper reports on the development of software in which mathematical algorithms apply geometric transformations to images in preparation for printing onto a rotating substrate. In support of this work, dimensional accuracy measurements of printed images and methods to correct radial print density variations are reported. The accuracy of printed images were found to be within ±0.2mm of their predicted size. The experimental work is briefly extended to the direct printing of plaster layers, formed by mixing two reactive ink solutions.Mechanical Engineerin

Health and development of children born after assisted reproductive technology and sub-fertility compared to naturally conceived children: data from a national study

In a non-matched case-control study using data from two large national cohort studies, we investigated whether indicators of child health and development up to 7 years of age differ between children conceived using assisted reproductive technology (ART), children born after sub-fertility (more than 24 months of trying for conception) and other children. Information on ART use/sub-fertility was available for 23,649 children. There were 227 cases (children conceived through ART) and two control groups: 783 children born to sub-fertile couples, and 22,639 children born to couples with no fertility issues. In models adjusted for social and demographic factors there were significant differences between groups in rate of hospital admissions before the children were 9 months old (P=0.029), with the ART group showing higher rates of hospital admission than the no fertility issues control group, the sub-fertile control group being intermediate between the two. Children born after ART had comparable health and development beyond 9 months of age to their naturally conceived peers. This applied to the whole sample and to a sub-sample of children from deprived neighborhoods

Rapid Design and Manufacture of Ultralight Cellular Materials

This paper details the design, manufacture and testing of regular metallic lattice structures with unit cell sizes in the range 0.8mm to 5mm and truss elements of 100-500 µm in diameter [1]. The structures were manufactured using Selective Laser Melting (SLM) technology from 316L stainless steel. Compression tests have shown yield loadings of over 3.5kN despite being only 18mm by 18mm by 10mm in height, the results are favourably comparable to current commercially available metallic foams. Software has been developed that creates slice files without the use of CAD software or STL files and is capable of producing lattices within a volume defined by a STL file.Mechanical Engineerin

Drape optimization in woven composites manufacture.

This paper addresses the optimisation of forming in manufacturing of composites. A simplified finite element model of draping is developed and implemented. The model incorporates the non-linear shear response of textiles and wrinkling due to buckling of tows. The model is validated against experimental results and it is concluded that it reproduces successfully the most important features of the process. The simple character of the model results in low computational times that allow its use within an optimisation procedure. A genetic algorithm is used to solve the optimisation problem of minimising the wrinkling in the formed component by selecting a suitable holding force distribution. The effect of regularisation is investigated and the L-curve is used to select a regularisation parameter value. Optimised designs resulting from the inversion procedure have significantly lower wrinkling than uniform holding force profiles, while regularisation allows force gradients to be kept relatively low so that suggested process designs are feasible

Automated Reasoning and Presentation Support for Formalizing Mathematics in Mizar

This paper presents a combination of several automated reasoning and proof presentation tools with the Mizar system for formalization of mathematics. The combination forms an online service called MizAR, similar to the SystemOnTPTP service for first-order automated reasoning. The main differences to SystemOnTPTP are the use of the Mizar language that is oriented towards human mathematicians (rather than the pure first-order logic used in SystemOnTPTP), and setting the service in the context of the large Mizar Mathematical Library of previous theorems,definitions, and proofs (rather than the isolated problems that are solved in SystemOnTPTP). These differences poses new challenges and new opportunities for automated reasoning and for proof presentation tools. This paper describes the overall structure of MizAR, and presents the automated reasoning systems and proof presentation tools that are combined to make MizAR a useful mathematical service.Comment: To appear in 10th International Conference on. Artificial Intelligence and Symbolic Computation AISC 201

The health and development of children born to older mothers in the United Kingdom: observational study using longitudinal cohort data

Objective: To assess relations between children’s health and development and maternal age. Design: Observational study of longitudinal cohorts. Setting: Millennium Cohort Study (a random sample of UK children) and the National Evaluation of Sure Start study (a random sample of children in deprived areas in England), 2001 to 2007. Participants: 31 257 children at age 9 months, 24 781 children at age 3 years, and 22 504 at age 5 years. Main outcome measures: Childhood unintentional injuries and hospital admissions (aged 9 months, 3 years, and 5 years), immunisations (aged 9 months and 3 years), body mass index, language development, and difficulties with social development (aged 3 and 5 years). Results: Associations were independent of personal and family characteristics and parity. The risk of children having unintentional injuries requiring medical attention or being admitted to hospital both declined with increasing maternal age. For example, at three years the risk of unintentional injuries declined from 36.6% for mothers aged 20 to 28.6% for mothers aged 40 and hospital admissions declined, respectively, from 27.1% to 21.6%. Immunisation rates at nine months increased with maternal age from 94.6% for mothers aged 20 to 98.1% for mothers aged 40. At three years, immunisation rates reached a maximum, at 81.3% for mothers aged 27, being lower for younger and older mothers. This was linked to rates for the combined measles, mumps, and rubella immunisation because excluding these resulted in no significant relation with maternal age. An increase in overweight children at ages 3 and 5 years associated with increasing maternal age was eliminated once maternal body mass index was included as a covariate. Language development was associated with improvements with increasing maternal age, with scores for children of mothers aged 20 being lower than those of children of mothers aged 40 by 0.21 to 0.22 standard deviations at ages 3 and 4 years. There were fewer social and emotional difficulties associated with increasing maternal age. Children of teenage mothers had more difficulties than children of mothers aged 40 (difference 0.28 SD at age 3 and 0.16 SD at age 5). Conclusion: Increasing maternal age was associated with improved health and development for children up to 5 years of age